2 plants, same pot, same strain, one deep green and beautiful, one yellow

The plants are about 5 weeks into flowering. They suffered a bit of a Mg deficiency in the first week and I gave them a small dose of epsom salts. That seemed to cure the brown spots and major yellowing. But the yellowing is back. That's not the wierd part. What's wierd is that I have two plants in the same pot because I accidentally planted two seeds in there. I thought I'd just see what happens.
One plant has always been a little taller and healthier looking, but that changed when we put them into budding and the taller one got more yellow and yellow and now I'm worried it won't make it to harvest. The wierdest thing is that out of all my plants, the healthiest one is the other one in the same pot as the yellow one. It has the darkest healthiest most robust leaves. The buds are unbelievable, just dripping with crysties. It's almost like the healthy one is sucking the life out of the yellow one. Is that possible?
One more thing relating to the rest of the plants, I know it's normal for yellowing to occur during budding, but is it supposed to be a uniform yellowing? It's a frustrating thing when a lot of fan leaves keep dying. i have a feeling they may need another dose of epsom salts cause the water here is so hard. Can that be harmful if that's not the problem?

hard water can be a problem some people get REVERSE OSMOSIS water or invest in an RO machine.

2 plants in 1 pot - bad idea - you nailed it in one sucking the life out of the other.


alot of people say keep your plants as green as possible i try to keep mine as green as i can without overdoing N . My plants tend to start yellowing around week 5. at this point i dont give them any high doses of N.


J

It's getting so far into budding that I would prefer not to give any more nutes. I think they'll survive. This was my first grow and I think I did pretty well, but I'm going organic next time.

I had yellowing problems right from when they went under a HPS. Started with heat stress, magnesium and nitrogen deficiency and now a life sucking death plant. The yellowing drives me crazy because of course I would like to have the greenest possible plants. Growing weed is a lot harder than I thought it would be. Well, hard to avoid any problems.

I think they're also root bound. I only put them in 3 gallon pots and let them get huge. I think that's a major problem. I'm going to shorten the cycle next time. Grow and Learn