seedlings not growing,puny!!!!WTF?

Hi All
This is my fifth grow and I'm having an absolute nightmare trying get my seedlings to grow.This is the second attempt at germinating seeds for this grow,on the first attempt all 30 of the Exodus Cheese seedlings died(Greenhouse Seed Co).They came up after about three days and they were the tiniest seedlings that i'd ever seen.The stem wasn't much thicker than a couple of human hairs and the first set of main leaves were microscopic.The cotyledon leaves turned a dark green colour and eventually curled over so I left the seedlings under a T5 flourescent light for around a week and they all eventually died.
I'm putting the seeds stright into rooting blocks(not rockwool),approx 10mm deep and keeping them in a vented propogator at around 75 to 80 degrees watering them with tap water.Like I mentioned before this is my fifth grow and i'm doing exactly the same as the previous four which were all very successful.
The second attempt at germinating for this grow(pics attached) looks like it's going the same way.I went out and bought 20 more seeds(costing another £180,that's £350 in all).5x AK47,5x Big Buddha Cheese,5 x Super Lemon Haze and 5 x Silver Cheese and they look like they're going exactly the same way(apart from the Silver Cheese which haven't come up at all.I'm gutted,feel like crying,just don't know what's wrong.In the pics they've been up for four days now and they're absolutely puny.It's not the seeds cos I've grown three of the strains before with no problems whatsoever.
I'm thinking it must be the tap water(although I used water straight outta the tap on my previous four grows with no problems whatsoever).I'm guilty of not letting the water stand so that the chlorine evaporates so what i'm asking is has anybody else had these problems before?I've had 100% success germinating around 120 seeds exacty the same way but just don't know WTF's going on here.I can only afford one more lot of seeds and then I'm broke.It must be the water.Any ideas?
If all of these seeds die which it's looking like they are,I'm gonna try germinating them on wet tissue paper with mineral water but i'd still like to get to the bottom of this problem first and maybe salvage some of these puny little things.
HEEELLLLPPPP!!!!

too wet.................damping off

you could use distilled water to be on the safe side but to me they dont look like there dying.

Those look like great little seedlings to me. I've grown exo cheese from greenhouse. The seeds were small, the seedlings were tiny but they performed just like any other plants. Assuming that you have not changed any of your equipment or technique, I would suspect that your humidity is too high. The dome on your propagator is not necessary and is preventing adequate airflow. So, yes, damping off is your most likely culprit.

Look TOO Wet, Let dry Out, Or ya damp off. What are your temps/humidity like.

Should save most if they dry out sum

Over watering and/or excess humidity from the looks of it.

Many thanks for your comments guys.Ok,they do look alright in the pics but when you actually see them they're absolutley puny and miniscule.The previous batch to this one looked exactly the same at this stage and they never grew,turned dark green and died.I forgot to mention in my first post that the seedlings have been coming up with yellow cotyledons as well.
I haven't had the lid on the propogator since the seeds popped so i don't think it's humidity,thats 40-50% and the temp's around 75 to 80 as well.
I'm hoping that this experiment with one cheese seed i had spare watering with mineral water only will improve things.Fingers crossed.

I've noticed "brand name" seeds are always tiny and the seedlings are half the size of ones from my own seeds. Kinda crazy to me you spend top money and get such tiny plants. They do eventually grow like normal though but whatever. I don't use a dome either for seeds, only clones. But you've already removed that. I'd try some bottled water instead of straight distiller, but that's just me. Maybe try a teensy but of nutes in the solution, I'm assuming those blocks have nothing. Even a 10% shot of nutes if nothing else.

they look good to me but they are over watered easy fix, apply good air flow.