Without knowing your type of league (Roto or H2H), it's a little hard to be very specific but having 4 of 8 SPs on the DL, with Smoltz just coming off can't be helping much. Assuming more or less standard scoring for your league, just W, K, SV, ERA & WHIP, nothing for IP, etc. For the season you should have about 53W, 547K, for 666IP. That's not much for most leagues to be anywhere near the top.
I had drafted Carpenter on one team but dropped him for another SP in early June. I also had another on DL for 3 wks. We had 3 - 5 SPs so losing two from the rotation had me falling further back each week. Replacing them got me back in the mix after a few weeks.
Re your staff, Johnson's good WHEN he pitches but 10 starts this year isn't good. right now he is probably on DL until early August. Sheets looks to be out until mid or late August. Gallardo's good but starting until Sheets returns, then bullpen. He's only pitched 28 innings this year. Carpenter probably isn't back until sometime in August, just had another rehab setback in his return. Don't know if you can designate a player(s) on DL in your league to open up a roster spot. If you can put one or more on DL, would certainly do so & pick up some SPs from waiver wire. Look for good IP, high K/9 ratio, 3-4 ERA.
If not, I'd drop R Johnson. He's not likely to get more than 10-12 more starts if there are no more injury problems. With Carpenter, you have to decide, if he returns end of August, how many starts will he get & how well recovered will he be. A big gamble. If I kept anyone & waited for them to come off the DL it would be Sheets. A finger problem is usually less serious than an elbow or back problem to a pitcher. Picking up 2 or 3 SP that are pitching regularly for your DLs will certainly help.
One other thing - most leagues have a qualifying or minimum number of AB (hitters) or IP (pitchers). Check your league. Your IP is low and if you don't make the minimum, you could lose scoring.
Let us know how things work out.