Red purple leaf stems

So far the plant has been growing great and looks excellent but i stilll think it could be doing better. I haven't seen much of a slowed growth but the older larger leaves (not many only about 4-5) turned yellow from the leaf tips inward until they were instantly white and then started to die in the same fashion, from tips to stem. I trimmed them as it happenedNow almost all my leaf stems exhibit a redish purple color mainly on the tops where light hits and the bottoms are still somwhat green. Is there something i can do to correct this? Could it be a deficiency of some sort? The leaves are dark green

nutelock or cold or some do it naturally. flush em just to be safe

Mine did it and I let it go until all the leaf stems were purple and than I did something. I first looked at nute lock witch is sometimes caused by a high PH and shure as shit my water PH had jumped above 7.5 something got in there. so I fixed that and also added DIY CO2 and stems were green and nice in 1 or 2 days.