first grow and having problems

hi all, this is my first grow iam only doing two ww plants under a 125w grow lamp they are nearly 4 weeks old to feed iam only using miracle grow and rain and tap water which ever ive got to hand, iam hoping someone could tell me why the tips of my leaves are turning yellow then dying please help any advice would be very grateful.

Tap water is purified with chlorine. Every1 knows tap water a the last source of water you should be using. & if you have to then I highly recomend you let the water air out for 24hours so all the chlorine molecules disolve. Chlorine kills your plant. The yellowing can be either you water too often & all the nutes are being released from the dirt too often causing a nute burn. Miracle grow has tons of nutes in the soil that are released everyone you water. Over watering suffocates your roots too.

How about more info so I can maybe pin point your problem a bit better.

that looks way too localized to be a chlorine problem. you only have two leaves that are yellowed. looks more like a chem or light burn to me. what kind of light are you using? do you have reflective material around your grow space?

and... i wouldn't say that tap water should be the last resort for growing. yes, it is true that there is chlorine in tap water and you should let it sit for 24-36 hrs to allow the chlorine chemical to evaporate out. but it's the cheapest source of water you can get. if you are doing a large grow, going out and buying gallons upon gallons of distilled water is crazy expensive. i know that's not the case here, but i am just being the devil's advocate.

i have never grown with anything but tap water and i've never had a problem. miracle grow on the other hand... that's just some bad news. next grow, dude, use a different soil. fox farm ocean harvest is my personal favorite.

tap water is fine to use. trust me alll you need to do is fill a 5 gallon bucket of tap water and let it sit outside for 2 days. the clorine in the water evaperates. 2 days later boom you have perfect grow water!!! oh n the yellow of the tips of your leaves is due to using miracle grow. great choice of fert but just tone it down a little bit and you should see a change in your plnts health in a fiew dqys of so. try trimming the dead/dieing leaves also!
burn it ayy

do not trim dead leaves ..until they are 100% dead and crispy..this can cause stress..id say like all the others its due to the miracle grow and possibly adding tap water without it being distilled...cut back on feeding the plant with shit and just let it grow for now...use clean or distilled water evry 2 days or so...this plant is a sativa id sai so its guna have a longer flowering period so lots of time to veg..cut back on nutes..theres plenty of time for that G'luck

thanks for all your input i will take this on board and at least i know for next time but do you think a 125w cfl grow lamp is ok its only a tiny closet i painted it white inside oh and its not miracle grow soil iam feeding it with miracle grow my soil mix is soil, sand, perlite, fert. How much longer till i have to go 12,12 iam on 18,6 at the moment. thanks again.