Please take a look at these pictures, nute burn? under/over water?

My plants have been in soil about 4 weeks. At first they grew very slowly (I think it was too cold) then they took off. But in the last few days the edges of the leaves have turned yellow/brown. After doing some research I decided to post pictures to get an expert opinion on my plants specifically. Thank you in advance!

looks kinda like nut burn, maybe to much phosphate? I dont know for sure.

Thank you! If it is nute burn should I just go back to plain water for a few days?

they are tiny for 4 weeks! some info on yur setup might help allot... lights, nutes, soil, ph, temps anything really

always give nutes on the size and look of the plants, not just time. just because someone says they need nutes at four weeks doesnt mean all plants. it depends on how the plants are doing individualy. back to plain water but not too much, they look wet enough now. what are you using to measure how much water is in the soil.
lu
dont use the finger in method, go by weight of the pot.