its not the end of the world, but its prolly why u nutrients are starting to lock up, it doesnt really need to be luke warm either round 70 degrees is good, u can get a tds meter that also reads temps of water for under 25 bucks now days, anyhow what ul want to do is invest in a good mycorrhizae innoculant, like great white or earth juice's biozeus, both are powder and can be mixed with water, either buy a gallon of filtered water or let ur water sit out for 24hrs (check with city water report to make sure its only chlorine and not chlorimine if it is chlorimine it wont evaperate and ul need to get filtered water til u buy a filter) add the mycorrhizae to the good water and water them in, that should take care of the problem as long as u keep those myco's alive and happy