Strange dark purple root tips on phal

[Fuzzy]

I bought this Phal Surf Song exactly a month ago. I chose it for its gorgeous roots and general health (thanks to the sticky post that was very helpful). The first picture shows the roots when I just brought it home. Well, for the first roughly 3 weeks the phal did nothing but bloom (it is still in full bloom and looking gorgeous). The roots all but stopped growing, there were no changes in them for 3 weeks. Then all of a sudden, about a week ago, all the tips started growing again, except they look very, very odd (see the last 2 pictures). First, they are very dark reddish-purple in color. Second, they have what looks like whitish specks on the tips. Finally, there's a chafing band-looking thing on the roots where the new tips are growing (second picture shows it best). What gives? Is there a problem with the phal? Is this fungus? Could it be a problem with my watering? Given that it's in sphagnum that dries VERY slowly, I basically give it about 4 oz of water every 10-12 days or so, but I mist the aerial roots daily from a spray bottle since the humidity here is quite low and the top dries out quickly.

I read somewhere that this could indicate the phal is getting too much sunlight. Should I lower the shade? The root tips that are buried in the medium look beige instead of dark purple. Bottom line: do you think there is any problem with the phal's roots? Anything I need to change?