Hi there
agree with figrat, but not with Obelix. Rhod looks anaemic to me, for a plant of this size probably 2-3 yrs old. I would say it's starving and perhaps dying...
Rhod will like a light loam, acidic but well drained (ner the gutter may be a wet plot). True for rain water as opposed to tap water, especially if calcareous.
Rhod also likes light, lot of ot. Perhaps the corner is a bit shadowy??
Check the above 2 factors before pouring feeding stuff, otherwise you won't get much more results.
If you transplant to another spot, consider trimming the branches after replanting: keep the strongest ones, cut all by 30% height. Allow re-sprouting, then fertilize to light doses.
Good luck!
AP