I thought I was doing everything right

My friend found some really good "dro" there was a couple of seeds in it,she decided to throw them in some dirt,a week later she was amazed because they started to grow,She gave me 3 plants,one died.I grew hydro before and I noticed a very fast growth rate compared to soil,I took the plants out of the dirt and I transplanted them to my bubbler,in the meantime I sprouted 7 other seeds that I had.Now I have nine plants in a 3 gallon bubbler(the plants that she gave me are about 4 weeks,my sprouted 7 are about 2 and a half weeks old).Right now they are under a warm 42 watt florescent that put out at about 150 and then there is another bulb which is a 15 watt flouro,They are under these light just until they get a little older and I have the 400 watt MH waiting for them alsp for flowering,I have a 360 watt HPS conversion bulb.My Ph is sitting at around5.5 to 6.0.right now it's 5.5.The TDS is sitting at 500,I have hard water coming into my house,it starts at around 350.I added 150food to bring my TDS up to about 520.Today I checked and it was floating between 490 and 500.One thing is odd that I noticed,I have an oakton ph meter I had it since last year,when I test the bubbler bucket,the measurment fluctuates badly,but when I test the ph in the ph meter cap I get an accurate reading.By my mearsurment my plants should be thriving but they are not ,they seem to be sick,could anyone give me a clue to what is going on.The ph is at 5.5 and the tds at 500.Also I am too broke to buy a RO machine and I ca't go to the store all the time buying distilled water,I let my water sit out for 24-t48 hours before use.Someone give me a clue please.I would love to taste that good ole taste of fresh homegrown herb again.TY

Well........here's a list of what you may not have done quite so right.

Your water at 350 is very, very hard. I think you need RO/distilled water and you already know this because you mentioned it.

I don't think I would try to keep plants of such different ages together as they should have completely different nutrient needs so you may well be overfeedng some and underfeeding others.....that way NOBODY gets the right amount.

I don't even know what to tell you to put your nutes at with two different ages plants in your setup so all I will say is......good luck with your grow. :)

Well is there a way that I can make my water "softer" at home without a r/o system.I have a water softner

You can try it but they tend to raise the sodium content of the water while removing the minerals you want such as calcium and magnesium which will cause deficiencies so water softeners generally aren't reccomended for hydro growing.

Well at least you have the ph down good..... :)