New grower plant problems

Hello everyone! This is my very first grow and I'm having some problems. I'm not sure if I'm posting in the right place so redirect me if I am. I'm exactly 14 days into the grow and haven't had a single problem till now. I'm using 2 T5 6500k tube lighting. I'm growing Sensi Seed Northern lights and some of my plants are getting brown spots and some of the edges are browning. I wasn't going to use nutrients till the third week but I read online that this could be a sign of a calcium deficiency so I decided to give them a mild dose of Liquid-Karma and Cal-mag last night. The temperature is always between 74-78 and humidity around 45%. I small fan inside blowing lightly on them and also have a typhoon fan outside the enclosure sucking in fresh air constantly. I transplanted the plants to the cups you see now from Styrofoam cups because I saw a root coming out of the bottom of one of the cups. They were in miracle grow seed starting soil and are now in Roots Organic original potting soil. The past 2 ph levels have been 6.4 & 6.5. Any idea what I'm doing wrong? The plant I mostly worried about is the last one that has severe leaf damage to the two bottom leaves. This all happened before I gave any nutrients. They seem to not be getting any worse sense I gave them the Cal-Mag and Liquid Karma but I really need to make sure I solved this problem. Please help thanks!

over-watered...........

All three of those plants look over-watered or just that first one? And over-watering causes brown spots?

2 and 3 really look it to me. dry them out a bit and re-assess, imo

and yes.........over-watering can cause brown spots and necrosis

One of the most common problems amongst first time growers. They drown their plants. Less is ALWAYS more.

It does looks like over watering but I would check the ph of your water/mix before adding it to plants then I would check the ph of the run off, I found a ph of about 5.5-5.8 worked better in roots mix. Make sure the the bottom of your cups have enough drain holes. Otherwise, you're off to a good start!

I would also be really carefull with using roots, in my current grow I found a really bad larvae problem in my run off.

Overwatering can look like nute burn. Usually stripping. The roots suffocate and the ball is small. Fungus gnats are a warning of this if you have any. As are droopy leaves. Up here rain causes it unless you up perlite to 50% in outdoor pots.

I started them in 8.5 fl oz cups but I started to see roots in 2 of the cups at the bottom so I transplanted them temporarily into 16 fl oz cups. My plants are looking much better but some of the leaves are still a golden brown color. Will post new pics soon.