When you say that you have problems holding my arms up to shoulder level for very long, even after a day of rest, is that because of a painful feeling in the muscle or your shoulder joints?
If it's muscular and in both shoulders then it sounds like your muscles are taking a beating but all is really OK. The extra volume is perhaps a little too much during the post 5s. If you are doing 2 exercises per body part (say chins and rows) in the same w/o, drop back to one and alternate until the end of the cycle.
If it's in your joints and/or ligaments (some form of -itis as O&G pointed out) then it's more likely that the extra volume with heavy 5s is starting to take its toll in a more serious way. This can take longer to heal and you would be wise to SD now.
Are you taking EFAs? I found that my joint pain during 5s and post-5s is now under control if I take a daily dose of a decent EFA blend (I use the Omega 3-6-9 from NOW®, described as an optimal blend of essential fatty acids sourced from organic Flax Seed, Evening Primrose and Olive Oils and expeller-pressed Wheat Germ Oil). I also take cod liver oil capsules with my evening meal. These helped keep any hip joint and rotator-cuff pain during 5s last cycle to an absolute minimum.
I am about to hit 5s for 4 sets this cycle for the first time but I will also be doing a 10 rep set to finish off each exercise. Perhaps you could try this next cycle too?
I really want to be able to extend the 5s this cycle so I will be monitoring joint pain closely and will back off the volume if it starts to rear its ugly head again. Hope you manage to sort yours.