i would be alarmed if this happend to mine! lol, glad you posted this tom. in regards to the watering seedlings question,im working on the theory that they must have to put up with the same amount of rain fall in the wild as there parents so ive let my seedlings grow solid for just over a full year now to get them to a size were they look like they can handle themselves.ill probably stop watering in june let them go dorment and bake in the sun. ill let you all know how many survive lol ben

Hello, bartleby1. I would check for the presence of mites. The new growth near the end of the stems shows what appears to be distorted growth. If you confirm, give the shrubs a taste of water from the hose at high speeds to dislodge them or use a miticide. The discoloration may be mite damage. Yes, if you have not seen blooms or flower buds opening by the end of June on a Macrophylla, you may not see bloomage from the old wood. If it is a rebloomer though, you may get blooms in July or so. If you need to prune, do it after the plant has bloomed but before the end of June.

in hindsight.. i dont understand the pic .... there is the obviously brown part i was speaking of ... but i cant tell if the rest of the pic has lesser browning.... or its a poor camera shot ... if the rest is also browning... you have some serious water issues ... either too much [your root rot theory] .. too little.. or improper planting .. or finally.. poor stock to begin with [like severely potbound] .... but.. having no history in regard to any of that.. i cant go further ... no one ever said two plants will react to transplanting the same way .... one would think so.. but one can not assume such .... [it kinda leads into the fact that one may have been poorer stock than the other at purchase????] ken

Hydrangea flowerheads can become discolored if the blooms are finished, they have been somehow damaged/bruised during transport or planting, if they have been scorched by sun or if they have had too much water directed on them. It is not a disease or insect problem but just something that occurs due to one or more of these factors. You can just remove them if you find the appearance unsightly but I wouldn't do any other pruning except just the deadheading, if you so desire.