Quite honestly Edrice the one area i suck at is injury, because i rarely ever get them, my only one was a tiny burst in my bicep quite a while back, and it fixed itself.
My suggestion is to just lay off it for a while, or not go as heavy, either way, if it hurts-stop.
Also go see a doctor, if its not muscle then its bone placement or possible trapped nerve, they could be able to fix/treat whatever it is.
I dont personally do much shoulder work, i just do a lot of incline chest work-builds out front delts real nice like you can see in my avatar, as for rear delts, i do backward dumbell flyes, find a hyperextension equipment, Hyperextensions are these
http://www.healthstylesexercise.com/catalog/images/2698_Nautilus_Hyperext_lg.jpg Hold that position(not the arms obviously i mean just the torso lol) (can be tough with weak backs, but by the looks of your weight/deadlift ratio-youll have NO trouble, and basically hold the dumbells with straight arms right below you, then very slightly bend the arms while raising the dumbells up kinda like a lateral raise-but obviously not the same motion, and get the dumbells as far behind you as you can, and bend your arms the same as a usual incline fly for chest-but doing it backwards obviously.
This gives MAJOR core and back strength to hold that position.
Use these 2 ways to get delts big-it should stop the pain but allow progress in strength/size in shoulders, i assume you can train traps with shrugs fine still?
Oh also-dont make a habit of maxxing deadlifts, its okay once every now and then to see where you are, but always try to stay above the 6 rep region, because it will stop possible injury.
The backs a temperamental thing, even with brilliant form-your back could just randomly ping and its gone, never happened to me, but ive heard it happen to people who usually do have very good form, and heavier weights can do that, so just always stay in the 6 rep limit for most workouts, or more than 6 reps you get what i mean lol.
1lbs up is great! Looks like the calorie increases are working!, hopefully this new weight will get you even more strength too!