I'm sorry, but this is so full of misinformation that I'm surprised. Those tips will probably lead to a completely wrong direction, not helping with the actual problem at all.
Firstoff, RA-4 is very tolerant to temperature and time variations, at least with Supra Endura. People have used it from 20C to 40C. I develop always 2 minutes at room temperature, which is from 23C to 25C. I've tried 1.5 and 3 minutes and that doesn't make a big difference at all. This all can be easily verified from many sources. Of course, it's best to be as consistent as possible, but this is not the source of the problems.
Then, mixed RA-4 developer keeps very well. The official instruction is probably something like a month (definitely not days! Check this if you don't believe me), but I've used almost one year old developer without any problems, as have many. (Mono-concentrated blixes, however, may be dead if the product has been on the shelf for a year or so.)
And finally, I think many if not most find drums tedious compared to simple trays. This is a matter of taste, but the fact is that using a drum will NOT solve the problems in question; in fact, drum can be even more difficult if there is a problem with excessive chemical carryover. So, if OP likes to work with trays, as many of us like, there's absolutely no need to adopt any new workflow.
Does the Arista kit have a single concentrate for blix? If so, it's probably the same kind of crap as Tetenal. I had yellowish/brownish staining problem with the Tetenal blix. It just has a shelf life of 6 months or so, as an UNOPENED concentrate! Buy the Kodak.
The example picture seems to have a bit of cyanish fog -- are you sure all the lights are completely blocked? Any red light might cause cyanish fog. Then, check the date of your paper. And, finally, that browniness might partially be caused by a faulty blix.